An anchored tanker sank off Vung Tau beach Tuesday morning, causing 388 tons of oil to spill into the sea.

Most of the oil was diesel. Water around the boat turned yellow and started to stink a couple of hours after the boat sank at 9:30 a.m. Many oil drums containing mucus oil fell into the water, some were fished out by local fishermen.

Local authorities surrounded the area, more than one kilometer from the shore, with more than 100 meters of buoys. But it didn't help keep the oil from spreading, observers said.

As of 1 p.m. Tuesday, the oil had spread into a 300-meter wide line, more than 18 kilometers long, according to Vung Tau Port Authority.

At the end of the day, the agency said divers had managed to patch up places in the boat where the oil was spilling.

The boat, which belonged to the state-owned Truong Sa Marine Products Company based in Vung Tau, sank upright with its prow still above water.

All 28 crew members had jumped from the boat and were saved by border guards and speedboats from the Vungtau Ship Company.